The costs for complex projects with one or more tasks can be estimated by examining input information or descriptions of the project. Such estimates are typically made by some assessment of total effort required (e.g., size of the final product) leading to a total estimate of hours or cost, typically based on judgments of the amount of information to be covered and the estimator's experience and subjective assessment.
Estimating systems exist for clearly specified projects, such as construction projects. Typically, estimates can be based on detailed construction plans and detailed specifications, leading to labor and materials estimates.